Valves of this type are frequently assembled in continuous coating units, designed for vacuum coating of flexible belt substrates, for example plastic foils, magnetic tapes, films etc., or also of rigid substrates, such as plastic or glass panes.
In is accordingly required, within certain time intervals, to introduce into the unit the belt substrates or foils, which are rolled in bales or foils, placing said substrates on a supporting axis, so that during the passage through the coating unit they may unroll from the bale.
Downstream of the coating chamber(s) another axis with a take-up drum is foreseen, on which the coated belt substrate is again being wrapped up.
Rigid substrates, placed on rollers, are continuously being transported between loading and unloading stations, which, on their turn, are being regularly ventilated.
Such continuous coating units are basically subdivided into modules (loading, coating and unloading module), which are sequentially disposed and interconnected by means of openings, through which substrate is being conducted into the subsequent module. It may be required to flood only one coating module, for example, in order to exchange a spray cathode or to accomplish other maintenance tasks, while the contiguous modules may preserve their present pressure level.
Therefore, reversible sluice valves are being integrated between the different modules. Thus, the volume to be exhausted after vacuum operations of the unit module, is being clearly reduced, since only individual stations are being ventilated and the other stations may remain in the evacuated condition. Evidently, in case of need, the entire unit may be ventilated.
Therefore, these valves do not have to continuously operate in a reversible fashion, i.e. bidirectionally, but lastly only have to be used or activated in case of changes of loads or other conditions of paralysation of the unit, in such case have to seal an existing pressure differential between atmospheric pressure and vacuum. The assembly position of these valves forcibly is directly in the area of the substrate transportation systems. In the case of glass coating units, these transportation systems are built as roller sections with definite roller distances. Due to continuously growing demand from clients, such as progressively smaller substrate dimensions and growing speed of passage, it is required to reciprocally shorten the distance of the different transportation rollers. This fact requires a very narrow separator or sluice valve, since it has to be integrated between two roller transporters, one roller transporter being provided in one module (upstream) and the subsequent roller transporter in the other module (downstream).
The document defining this feature DE 198 57 201 A1, describes such a plane sluice valve for simultaneous blocking or release of two reciprocally aligned passage openings, foreseen between two vacuum chambers, which feature a smaller height and larger width. The valve is designed for continuous coating units of large glass formats.